Belgian police has been conducting large-scale raids in Brussels in a search for suspects in Tuesday's attacks, which claimed the lives of at least 31 people and left hundreds injured.

The attacks started with twin bombings at the departure hall of Zaventem airport, where at least eleven people were killed and up to a hundred other wounded.

About an hour later, an explosion occurred at Maelbeek metro station near the European quarter of Brussels, in which at least twenty people lost their lives and 130 other suffered injuries.

It is believed that the two explosions in the airport were caused by suicide bombers blowing themselves up, while it is still unclear whether this was the cause of the blast at Maelbeek.

A suspect was caught on security cameras at the airport next to two men pushing trolleys, who are thought to have been the suicide bombers blowing themselves up.

The third man, dressed in light-coloured coat and a hat, is believed to have fled the scene after his bomb failed to detonate.

An unexploded bomb and Kalashnikov rifle were reportedly found at the airport, with the police having defused the bomb.

Islamic State (IS) claimed responsibility for the attacks in a statement released by a news agency affiliated to the terrorist group.

The attacks come only days after the chief suspect in last year's November 13 attacks in Paris, Salah Abdeslam, was detained during a police raid in the Brussels suburb of Molenbeek last week.

During a raid in the northern Brussels suburb of Schaerbeek on Tuesday, police found chemical products, IS flag and an explosive device containing nails.

Brussels has started to slowly recover after Tuesday's lockdown, but the airport is expected to remain closed at least until Thursday, while the metro will run a reduced service on Wednesday. Three days of national mourning have been declared in Belgium.